Acetylene manufacture



April 17, 1951 Filed Nov. 8, 1948 S. F. ROBINSON ACETYLENE MANUFACTURE 2 Sheets-Sheet l SNIMDVBO sfP. ROBINSON A T TORNE YS April/117, 1951 s. P. RcJBINsoN `2,549,240

ACETYLENE MANUFACTURE Filed Nov. 8, 1948 2 Sheets-Sheet 2 INVENTOR.

S. P. ROBINSON BY i! A TTORNE YS Patented Apr. 17, :1951

ES PATENT OFFICE ACETYLENE MANUFACTURE SamP. RobinsomBartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application November 8, 1948, Serial No. 58,893

Claims. (Cl. 260-679) ThisV invention relates to vthemanufacture of acetylene. In 4another aspect this invention re'- lates to the manufactureof acetylene fromI a hy-I In another aspectV this invention drocarbon gas. relates `to the efficient conversion of a hydrocarbon gas to acetylene, in high yield. n

Acetylene has many industrial uses. Acetylene is used directly or indirectly in the manufacture of aldehydes, acids, polymerization products, and various other compounds. `Various methods have been proposed for the manufacture of acetylene. Perhaps one of the oldest methods for making acetylene is its manufacture from calcium carbide. Other well-known processes for acetylene manufacture include such as electric processes employing the heat 4of an electric arc, the partial combustion of hydrocarbons, the pyrolysis of hydrocarbons, and the recovery of by-product acetylene from other commercial processes such as thermal or catalytic cracking of hydrocarbons. Among the processes proposed heretofore, acetylene has, in many instances, been produced only in uneconomical and limited yields.

Since acetylene is Very active chemically and is the basic material for the manufacture of many organic compounds, the cost of the manufacture of acetylene is of major importance, and this invention is concerned with a process wherein acetylene is economically manufactured from `a gaseous hydrocarbon material in high yield and at a high conversion efficiency.

An object of this invention is to provide a process for the manufacture of acetylene.

Another object is to utilize hydrocarbons `in the manufacture of acetylene. n

Another object is to provide a process for the conversion of a hydrocarbon to acetylene in high and selective yields. l n

Other objects will be apparent, to one skilled in the art, from the accompanying discussion and disclosure.

In accordance with this invention, acetylene is produced by first cracking a hydrocarbon gas to form ethylene in selective and high yield, and then admiring the total hot cracking-product with added hydrogen heated to a temperature above the hydrocarbon cracking temperature, and the resulting hot cracking-product-hydrogen mixture passed through a bed of titanium dioxide catalyst, whereby acetylene is formed in high yield and recovered in a subsequent series of purification steps. 1 n

In a preferred embodiment of my invention the hydrocarbon cracking step and the hydrogen heating step are each conducted in a separate pebble heater apparatus, eachof which, in the practice of my invention, may comprise a series of substantially vertically extending zones often in vertical alignment with each other. Usually two such zones are employed and are connected by a relatively narrow connecting zone, or throat. The top or upper zone is commonly referred to as the pebble heating chamber. and the lower zone as the gas reaction or gas heating chamber. A combustion zone or chamber is positioned adjacent or in close proximity tothe sides of the lower portion of the heating chamber. Combustion gas from a combustion chamber is passed through the mass of pebbles in the pebble heating chamber. A contiguous mass of particulate contacting material, often referred to as pebbles, lls the pebble heating zone, the connecting zone or throat, and the gas reaction zone, and flows downwardly through these zones by force of gravity. Pebbles are discharged from the bottom of the gas reaction zone at a controlled rate and returned, usually by elevating means to the inlet in the up` per portion of the pebble heating zone and on into the pebble heating chamber. A contiguous moving pebble mass thereby lls the pebble heat-v ing zone, gas reacting or heating zone, and the interconnecting zone, or throat at all times.

The term pebble as used in this specification denotes any refractory material in fluent form, size and strength, which will flow readily by gravity through the various chambers of the pebble heater apparatus. Pebbles are preferably substantially spherical, and are about 15 of an inch to 1 inch in diameter, the preferred range being 1/4 inch to 1/2 inch.

In the following description, one method of operating my process will be specifically disclosed. The figures are diagrammatic illustrations of apparatus in which my process may be practiced. It is to be understood that the flow diagram is diagrammatic only and may be altered in many respects by those skilled in the art and yet remain Within the intended scopeof my invention.

Figure 1 is a schematic flow diagram of a preferred process of my invention. Figure 2 is a detailed diagrammatic illustration of a portion of apparatus only briefly illustrated in Figure 1. Referring to Figure l, in pebble heater apparatus I, pebble heating zone I4 and gas reaction zone Il are insulated chambers, each containing a contiguous uent mass of pebbles 9 and connected by a heat insulated conduit, forming pebble throat I6. Conduits 'I and B serve as pebble inlet and outlet for chambers I4 and II, respectively. Star valve (or other type of pebble feeder) I8 regulates the rate of iiow of pebble mass 9 through chamber I4, throat',V I6 and chamber II, and feeds pebbles flowing from the bottom of chamber II into bucket elevator I9 for delivery into pebble inlet 'I and on into chamber I4. Combustion chamber `'lll is positioned subjacent pebble heating chamber I4. Chambers I4 and 20 are separated by perforate support 25 through which combustion gas formed in chamber 2liy ascends to pass in direct heat exchange relation with pebble mass 9 in chamber I4. Fuel gas, usually natural gas from line 6 and/or hydrogen recycle gas from lines I3 and 24, described hereafter, is introduced through line 22 and admixed with oxygen, or an oxygen containing gas, preferably air, from line to form a combustion mixture in line 23 which is burned in combustion zone '20. I-Iot combustion gas formed inV zone 20 ascends through perforate support 25 at a temperature selected to heat pebbles in chamber I4 to a temperature suflicientlyk above a predetermined temperature of a subse- Y quent cracking stepdescribed hereafter, so that the cracking reactants are brought to the'requisite temperature in a very short time and maintained at such a level for the requisite time. Suchra required pebble temperature is usually within the Vrange of from 1400 to 2800o F., and is regulated byY the f combustion gas temperatureV which'in turn' is dependent on the specific components ofthe combustion mixture and the proportions'of oxygenjtherein, and by the rate of pebble `flow through chamber I4. Combustion gas having impartedheat to pebbles inA zone I4 i's, passed as eiuent from zone I4 through line I1 to ,further utilization, not shown. Ethanepropane cracking stock, containing a relatively high proportion of ethane to propane, is introduced into the lower portion of gas reaction chamber II through lines I0 and I5, entering at a point below gas distribution plate 4, and is passed through chamber II in direct heat exchange relation with pebbles previously heated in zone I4 to a temperature sufficiently high to heat the cracking stock to a temperature within the range of 1400 to.2000 F. and to maintain that temperature level for a contact time within the range of 0.05 to 1.5 seconds whereby cracking takes place to produce an ethylene-rich cracking product. Pressure conditions within the pebble heater apparatus I are preferably above atmospheric. Pressures from 0 to 5 p. s. i. g. are often utilized, although a pressure as high as p. s i. g. may be employed, in some cases. Eiiluent gas from reaction chamber I I comprises ethylene-rich cracking product which is passed through line I2 to a mixing T or venturi 28 wherein it is quickly mixed with and further heated by a hydrogen-rich recycle stream from a subsequent purification step, previously heated to a temperature above the cracking efliuent temperature, in the 4gas heating chamber of pebble heater apparatus II. Pebble heater apparatus II may be mechanically similar to pebble heater apparatus I, and kis so illustrated.A Portions Vof pebble heater II corresponding to numbered por-Y tions of pebble heater I are numbered identically except that the character a is added to identify that portion as a part of pebble heater II. Pebbles in chamber I4-a are heated in the same manner as already described for heating pebbles in chamber I4, to a temperature above the predetermined temperature of a subsequent heating step in heating chamber II-a.

Hydrogen-rich recycle gas from a subsequent purication step described hereafter, in lines 26 and 24 is introduced into the lowerY portionv of gas heating chamber II-a. entering at a point below perforate gas distribution plate le-a, andis vpassed therethrough in direct heat exchange relawith eiiiuent cracking gas product from chamber II entering from line I2', in a volume ratio to cracking gas productl within the limits of from 1:1 to 10:1, to form a hydrogen-cracking product admixture at a temperature within the limits of 2000 to 2600 F. A hydrogen-cracking product admixture from venturi 28 is passed at its existing temperature to catalyst chamber 129 and through a fixed bed of highly calcined titanium dioxide catalyst 3I contained therein, for

a reaction time within the limits of 0.01 to 1.0 v

second. Eiuent from catalyst zone 23 is passed through line 32 and quickly quenched by contact with water injected directly into line 32 from line 33, to a temperature Vbelow1000o F., above which some undue polymerization and/ or dehydrogenation of acetylene may take place. Preferably, material in line 32 is quenched to about 350 F. This may be effected by means of the water quench already described. However, if desired, material from line 32, quenched as already described, may be passed through lines 34 and 35, to heat exchange means31, usually a waste heat boiler, and therein cooled to the desired temperature, usually about 350 F., in indirect heat exchange with water. Eiuent from cooler 31 is then passedV through lines 38 and 39 to tar trap 42'. If desired, materialfrom line 34 may be passed directly to line 39 through line 4I. Gas

in line 39 is passed tangentally into trap 42V wherein viscous and solid tarry materials are removed. Off gas from tar trap 42 may contain small carbon particles not arrested in trap 42 and is passed through line 43 to carbon collection system 44 comprising any one of a number of known carbon arresting means such as various filter means, Cottrell apparatus, or the like. I prefer a system employing ber glass bag iilters subject to shaking and/or oil washing, such an arrangement being well known to those skilled in the art. Carbon is removed from the gas in zone 44, and carbon-free off gas therefrom is passed through line 46 to water quench tower 41 and passed in countercurrent flow therein to downwardly flowing water or water spray inV troduced through line 48 and discharged through line 49. Eiiiuent gas from quench zone 41 is discharged ata temperature of from about F. more often about 120 F. Gas from quench zone 41-is then passed through line 50 to an absorber-stripper `system of conventional design, employing absorbent of the mineral seal oil type. Gas from line 50 is introduced to absorber 5I and passed in countercurrent ow therein to downwardly owing stripped and/or fresh mineral seal oil whichabsorbs all materials from the gas, heavier than propane, which materials are formed in small quantities in catalyst zone 29 as by-product. Enriched absorber oil is passed from the lower portion of absorber 5I through line 52 to stripper 53 and maintained therein under distillation or stripping conditions whereby the rich oil is separated from its absorbed materials. Lean absorber oil is passed from stripper 53 through lines 54 and 53 into the upper portion of absorber 5I. Fresh absorber oil is added, when desired, to line 56 and line 5,41. Materials heavier than propane, desorbed from absorber oil in stripper 53 are passed therefrom through line 58 to product separation means`59 comprising coolers, separators, distillation equipment, storage tanks and the like not individually illustrated, which can berused to effect a separation of various selected fractions from the propane and heavier materials intros. duced through line 58. From separation means '59 are Withdrawn normally gaseous hydrocarbons through line 6I, benzene through line 62, toluene from line 63, diolen hydrocarbons from line 64, and selected heavier aromatic materials from line 66. Unabsorbed gas from absorber I is passed through line 61 to charcoal adsorption unit 68 wherein a hydrogen fraction containing hydrogen in an amount of from 40 to 100 per cent, more often from 40 to 80 per cent and an acetylene-rich residual fraction are separated. `A hydrogen -rich gas containing methane as the heaviest component is passed from charcoal adsorption unit 68 through lines 69 and 24 for recycle through line 2'6 to pebble heater chamber I I -a and, when desired, to combustion chamber and/or combustion chamber 2li-a through line I3, as already described. Any excess hydrogen-rich recycle gas in lines 69 and 24 may be withdrawn through line 1I for other utilization, not shown. Charcoal adsorption means 68 as employed herein, is well known to those skilled in the art, and employs the principle of selective adsorption of hydrocarbons by a moving bed of activated carbon particles, with the subsequent removal of the adsorbed hydrocarbon by heat and steam, and is especially well applied to the separation of the materials from line 61 as already described. An acetylene-rich fraction containing some ethane and ethylene and still smaller amounts of propane and propylene is desorbed from the activated carbon in adsorber 68 and passed through line 12 to an absorber-stripper system employing acetone as an absorbent. Material in line 12 is introduced to absorber 13 and passed countercurrently therein to downwardly flowing stripped and/or fresh acetone introduced through line 16 whereby acetylene is substantially completely selectively absorbed in acetone. Enriched acetone is passed from absorber 13 through line 14 to stripper 11 wherein under distillation conditions of pressure and temperature, acetylene is desorbed from the rich acetone absorbent. Lean acetone absorbent `is returned to absorber 13 through line 16. Fresh acetone may be introduced to the system through line 19. Residual gas comprising ethane in a major proportion together with relatively small amounts of ethylene, propylene and propane is recycled through lines BIJ and I5 to gas cracking chamber II in admixture with fresh feed from line I0. Overhead from absorber 13 may be recycled and reacted to extinction. Acetylene product of high purity separated in stripper 11 is passed therefrom through line 8| and recovered in high yield, as product of the process.

For convenience and clarity certain apparatus, such as pumps, surge tanks, accumulators, valves, etc. have not been shown in the drawing. Obviously such modifications of the present invention may be practiced without departing from the scope of the invention.

Figure 2 is a diagrammatic cross sectional view of a preferred arrangement and construction of venturi 28, catalyst zone '29 together with lines I2 and 21 by means of which I may conduct the mixing step and reaction step of the process of my invention, at .the required high temperature conditions and gas velocities. Referring to Figure 2, eiuent line I2 is rigidly attached to venturi 28 by flange 9|. Line 21 and reactor 29 are rigidly attached to venturi 28 by flanges 92 and 93 respectively. Lines I2 and 2'1, venturi 28 and reactor 29 are all highly insulated and maintained in close proximity to each other to minimize heat losses, prevalent at the temperatures employed in those vessels. Line I2 may be lined with a dense, hard-burned, small grained, high purity, supported alumina lining 94 to resist abrasion, and this lining is backed by a light-weight mullite or alumina insulating material 96. Outer jacket 91 may be any suitable alloy steel. Reactor 29 may be fabricated of the same materials as line 21 already described. The lining.

of venturi 28 is fabricated preferably of alumina I UI, but of a very small grain, dense, hardburned structure to resist abrasive effects resulting from high gas velocities. Outer shell 91 of lventuri 28 may comprise any suitable alloy steel.

The TiO2 catalyst employed in the practice of this invention is preferably a precipitated gel type catalyst. Various procedures are well known for preparing such a catalyst. I may prepare the catalyst employed in .this invention by coprecipitating Ti(OH)4 and A1(OH)3 gels in which the ratio of T102 to A1203 may usually be in the range of from 0.01 to 030:1. The precipitated mixture is dried, then extruded, generally into pellets, and calcined at a temperature within the range of 2600-3000 F. for a duration of from 2 to 12 hours, preferably 2 to 6 hours. Generally, I prefer to calcine the TiO2 catalyst at about 26000 F. for from 2 to 6 hours. An alternate means of preparing a Ti02 catalyst suitable for use in the practice of my invention is to form spheres from commercial rutile (TiOz) and plasticizing ball clay, and calcining the resulting spheres at a, temperature of about 2600D F. for a duration of from 2 to 12 hours, preferably 2 to 6 hours. The preferred 'IiOz content of the gel type catalyst may usually be varied from 5 to 25 per cent, and the TiO2 content of the spheres formed from rutile and ball clay may generally be from 70 to per cent.

I am not certain of the mechanism of the reactions taking place during the formation of acetylene in the practice of my invention. However, there are apparently at least 3 reactions taking place simultaneously at this stage, as indicated by the following equations.

1. Partial dehydrogenation of ethylene to acetylene 2. Dehydrogenation of acetylene to carbon and 3. Polymerization of unsaturates C2H4+C2H2 C4H6 The rate of reaction l is highest, followed in order by reactions 3 and 2. To obtain high acetylene yield it is necessary to employ the necessary high temperature and a contact time sufficiently long to favor formation of large quantities of acetylene, but at the same time to employ the least drastic conditions of temperature and time, in order that appreciable decomposition and polymerization reactions of the types suggested by Equations 3 and 2 do not occur, or for that matter, to minimize any side reactions resulting from any degree of dehydrogenation and/or polymerization. I have found that I may minimize such dehydrogenation and/ or polymerization side reactions by conducting my acetylene-forming reaction in the presence of a highly calcined TiOz catalyst described more fully hereafter. I have found that by employing an active TiOz catalyst calcined at a temperature of about 2600 to `3000" F. for 2 to 12 hours, whereby I presumably reduce catalyst activity and surface area, I may form acetylene from the ethylene-containing crackingproduct at temperatures signicantly lower than those normally required when forming acetylene from ethylene in the absence of a catalyst. By this practice, I apparently have decreased the rate of the reactions of the types illustrated by Equations 2 and 3 to a disproportionately greater extent than I have decreased the rate of the preferred reaction indicated by Equation l. Employing such a TiOz catalyst at thetemperatures already described, I have provided for a high conversion of preformed 'ethylene to actylene in a minimum of reaction time.

By conducting the acetylene-forming reaction f in the presence of excess diluent hydrogen I have buifered undesirable side'reactions and, at the same time, have reduced hydrocarbon V,partial pressures in the reaction zone. By the utilization of diluent hydrogen I have definitely minimized the extent and occurrence of undesirable side reactions taking place in the acetylene-forming step. I further utilize the hydrogen-rich recycle stream as a heat carrier, as already described, by means of which I am able to quickly raise the temperature of the ethylene-rich cracking product to the requisite reaction temperature. Furthermore, by utilization of such hot hydrogenrich recycle gas I maintain the temperature drop across the catalyst bed, and carbon deposition on the catalyst, at a minimum. Furthermore, by using hot hydrogen as a diluent and heat carrier instead of, for example, steam, I utilize a byproduct stream of low fuel value, instead of a more costly material that would necessitate additional capital investment. Accordingly, by eliminating the use of steam diluent I prevent the formation of undesirable carbon oxides occurring from any water-gas reaction, i. e., the formation of CO and CO2 by reaction of steam with hydrocarbon, which formation decreases the acetylene yield, abets corrosion and hinders purification of the initial acetylene product.

By employing the charcoal absorption unit, as already described, separation of hydrogen and methane from the product gas is precise regardless of the quantity oi hydrogen by-product, and

substantially no acetylene is present in the recycled gas. Consequently, large scale hydrogen dilution as practiced in my invention is in no way harmful to ultimate recovery of acetylene product.

In the practice of the process of my invention, I utilize temperatures significantly below those employed in the manufacture of acetylene non-catalytically from an ethylene-rich gas, and consequently I may employ commercial scale equipment which can be fabricated of less expensive materials.

My invention will be further illustrated and defined by the following example. The reactants and their proportions and other specific ingredients are presented as being typical and should not be construed to limit the invention unduly.

Example A mixed ethane-propane depropanizer overhead from natural gasoline plant operation having the following composition:

is cracked in the gas reaction chamber of a pebble heater apparatus at a temperature of 1700" F. for a contact time of 0.25 second to produce cracking product having the following composi- ,At the same time, a hydrogen-rich recycle gas stream, described hereafter, containing 73 per cent hydrogen and 27 per cent methane by volumev isheated to 2700 F., for 0.15 second in the gas heating chamber of an auxiliary pebble heater. Under these heating conditions the methane is partially cracked producing a gas of the following composition:

Component:

Hydrogen volume per cent 1 76.0 CH4 do 21.2 C21-I2 do 2.8 Carbon and tar weight per cent 7 1 Carbon and tar-free basis.

The eliiuent cracking-product and heated hydrogen-rich recycle streams are mixed in a high velocity Venturi throat and the resulting admixture passed vertically downward therefrom into a catalyst chamber packeolrwith lg calcined 'IiO2 catalyst pellets of the precipitated gel type, containing 7 per cent by weight TiOz. Approximately 2.55 standard gas volumes yof the heated hydrogen recycle gas is required per volume of cracking eiiiuent, for heating. With higher ethane concentrationsv in `the admixture passed Y from the Venturi mixing throat, less heated hydrogen recycle gas would be necessary. The approximate composition of the admixture being passed from the Venturi mixing throat to the catalyst chamber, but before passage through the catalyst chamber is as follows:

Component: Volume per cent H2 59.8 CI-Lr 23.4

C2H2 2.4 C21-I4 9.3

CsHs C4-i- 3.3

Gas is passed from the Venturi mixing throat at a temperature of .2200o F., through the catalyst bed for a contact time of 0.10 second. Total gas product leaving the catalyst bed has the following approximate composition:

Component:

H2 volume per cent 1 64.5 CH4 do 24.3 C2H2 d0 6.3 C21-I4 d0 1.9 C21-ls do 0.2 03H6 do 2.8 Tar and carbon weight per cent 7.0

1 Carbon and tar-free basis.

Effluent product gas from the catalyst chamber is quickly quenched by direct water injection whereby it is cooled in a very short time to a. temperature below about 1000 F., under which conditions polymerization and dehydrogenation of acetylene in the reaction product is substantially prevented. The partially quenched gas is further cooled to a temperature of about 350 F. in a waste heat boiler. Quenched gas is then passed tangentially into a tar trap wherein tarry materials are separated andthen vto a carbon l collection system comprising ber glass bag filters. The partially cooled gas upon being passed from the bag filters is passed into a water quench ty-pe hydrocarbons, light aromatic hydrocarbons such as benzene, toluene, xylene, and various heavier aromatics. The propane and lighter gas components, unabsorbed, are passed from the absorber column to a moving bed type carbon absorption tower, wherein a hydrogen-rich :gas containing methane and a residual acetylenerich gas Cz-Cs product fraction are separated. Hydrogen-methane gas containing 73 per cent hydrogen and 27 per cent methane is passed from the carbon absorption tower and is recycled to a gas heating chamber of a pebble heater, and ultimately to the reaction, already described. The residual Ce-Cs fraction contains about 76 per cent- C2H2, 22 per cent C21-I4 and 2 percent other C2-C3 hydrocarbons, and is passed to an absorber system employing acetone absorbent wherein acetylene product is selectively adsorbed. Non-acetylene hydrocarbons are recycled to the cracking step, already described. The acetylene-rich acetone absorbent is stripped, and acetylene is recovered as a product of the process.

As will be evident, to those skilled in the art, various modications of this invention can be made or followed in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the claims.

I claim:

1. A process for the manufacture of acetylene, comprising contacting a mixture of hydrogen and ethylene with a catalyst consisting essentially of titanium dioxide at a temperature within the limits of 2000 to 2600 F., and for a contact time of from 0.01 to 1.0 second, whereby acetylene is formed; said catalyst having been previously vcalcined at a temperature of from 2600 to 3000.3 for a duration of from 2 to 12 hours so as to` effect suitable activation for dehydrogenation of ethylene to acetylene, and recovering said acetylene as a product of the process. g

2. A process for the manufacture of acetylene, comprising contacting a mixture of ethylene and hydrogen with a catalyst consisting essentially of titanium dioxide at a temperature within the limits of 2000 and 2600 F. for a contact time iwithin the limits of 0.01 and 1.0 second, wherebywaceftylene is formed, and recovering said acetylene as a product of the process.

3. A process for the manufacture of acetylene.

comprising introducing hydrogen in admixture with ethylene into contact with a catalyst consisting essentially of titanium dioxide, for a contact time of from 0.01 to 1.0 second, and at a temperature within the limits of 2000 and. 3600 F., whereby acetylene is formed; said catalyst having been previously calcined at a temperature of about 2600 F. for a period of from 2 to 6 hours, and recovering said acetylene as a product of the process.

4. The process of claim 1 wherein said catalyst l is a precipitated gel type catalyst containing from 5 to 25 per cent by weight TiOz.

5. The process of claim l wherein said catalyst is prepared from rutile and a plasticizing clay, and contains from 70 to 95 per cent by weight of TiOz. 6. The process oi claim 1 wherein said catalyst is disposed as a xed bed and wherein said mixture of hydrogen and ethylene is passed through said fixed bed at an initial temperature in said range of 2000 to 2600 F., and wherein effluents from said fixed bed are quickly quenched to a temperature below 1000 F.

7. The process of claim 1 wherein said mixture of hydrogen and ethylene is formed by admixing a stream of ethylene-rich product of hydrocarbonA cracking with a hydrogen-methane stream containing from 40 to 80 volume per cent hydrogen, and wherein the volume ratio of said hydrogenmethane stream to said ethylene-rich stream is within the limits of 1:1 and 10:1.

8. The process of claiin 7 wherein said volume ratio is within the limits of 2: 1 and 6:1.

9. A process for the manufacture of acetylene, comprising passing a mixture of hydrogen and ethylene at an initial temperature .within the limits of 2000 and 2600 F. through a fixed bed of `catalyst consisting essentially of granularI titanium dioxide previously calcined at a temperature of from 2600-3000 F. for a period of from 2-12 hours, at a contact time of from 0.01 to 1.0 second, and at a pressure within the limits of 0 to l5 p. s. i. g., whereby acetylene is formed together with by-product hydrogen, separating acetylenecontaining product thus formed into a hydrogenrich fraction and a residual acetylene-rich fraction, recycling at least a portion of said hydrogenrich fraction as part of the above said mixture of hydrogen and ethylene, and recovering acetylene from said acetylene-rich fraction.

10. The process of claim 9 wherein said hydrogen-rich fraction contains from 40 to 80 volume per cent hydrogen.

SAM P. ROBINSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Namel Date 1,995,136 Winkler et al Mar. 19, 1935 2,030,070 Morrell Feb. 11, 1936 2,167,471 Auerbach July 25, 1939 2,389,636 Ramseyer Nov. 27, 1945 FOREIGN PATENTS Number Country Date 470,258 Great Britain Aug. 9, 1937 750,496 France' May 29, 1933 823,303 France Oct. 11, 1937 

2. A PROCESS FOR THE MANUFACUTRE OF ACETYLENE, COMPRISING CONTACTING A MIXTURE OF ETHYLENE AND HYDROGEN WITH A CATALYST CONSISTING ESSENTIALLY OF TITANIUM DIOXIDE AT A TEMPERATURE WITHIN THE LIMITS OF 2000 AND 2600* F. FOR A CONTACT TIME WITHIN THE LIMITS OF 0.01 AND 1.0 SECOND, WHEREBY ACETYLENE IS FORMED, AND RECOVERING SAID ACETYLENE AS A PRODUCT OF THE PROCESS. 